DescendantIterator.java
///////////////////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
// Copyright (C) 2001-2022 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
///////////////////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.xpath.iterators;
import java.util.LinkedList;
import java.util.Queue;
import net.sf.saxon.om.AxisInfo;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.tree.iter.AxisIterator;
import net.sf.saxon.tree.iter.SingleNodeIterator;
/**
* Recursive-free implementation of the descendant axis iterator.
*/
public class DescendantIterator implements AxisIterator {
/**
* Enum defines starting node for iterator.
*/
public enum StartWith {
/** Start with current node. */
CURRENT_NODE,
/** Omit current node and start with child nodes. */
CHILDREN,
}
/**
* Queue for sibling nodes.
*/
private final Queue<NodeInfo> queue = new LinkedList<>();
/**
* Descendant axis iterator.
*/
private AxisIterator descendantEnum;
/**
* Create an iterator over the "descendant" axis.
*
* @param start the initial context node.
* @param startWith mode of the iterator, see {@link StartWith}.
*/
public DescendantIterator(NodeInfo start, StartWith startWith) {
if (startWith == StartWith.CURRENT_NODE) {
descendantEnum = SingleNodeIterator.makeIterator(start);
}
else if (startWith == StartWith.CHILDREN) {
descendantEnum = start.iterateAxis(AxisInfo.CHILD);
}
else {
descendantEnum = null;
}
}
/**
* Get the next item in the sequence.
*
* @return the next Item. If there are no more nodes, return null.
*/
@Override
public NodeInfo next() {
NodeInfo result = null;
do {
if (descendantEnum == null) {
if (queue.isEmpty()) {
break;
}
descendantEnum = queue.poll().iterateAxis(AxisInfo.CHILD);
}
else {
result = descendantEnum.next();
if (result == null) {
descendantEnum = null;
}
}
} while (result == null);
if (result != null) {
queue.add(result);
}
return result;
}
}